Sound re-recording method and system



`Iuly 28, 1953 K. SINGER SOUND RES-RECORDING METHOD AND SYSTEM Filed Aug. 22, 1950 f1 AWN IN VEN TOR. l Kuri? Singer BVM/@W Patented July 28, 1953 SOUND RE-RECORDING METHOD AND SYSTE Kurt Singer, North Hollywood, Calif., assignor to Radio Corporation of America, a corporation of Delaware Application August 2z, 195o, serial No. 180,747

9 claims. (ol. 17o-100.3)

This invention relates to sound record production, and particularly to systems for the production and/or duplication of photographic sound track records.

The production of photographic sound tracks, particularly for combination with concomitant motion pictures, is well-known. I'hese tracks are of various types, such as variable area and variable density, the variable area type of track being in different forms, such as uni-lateral, bilateral, Class A push-pull, Class B push-pull, and others. Noise reduction is usually applied to photographic sound tracks either by a shutter or by a biased light beam, although certain forms of photographic tracks, such as Class B pushpull, are inherently noiseless. Usually, the sound tracks are first recorded as a negative at a certain edge of the film, so that when contact printed emulsion to emulsion to obtain the composite closed and claimed in Dimmick U. S. Patent No. 3U

2,311,159 of February 16, 1943. Because of the optical system used in this form of track, anticipatory noise reduction may be obtained to avoid clipping. Clipping is the result of noise reduction action not reacting fast enough to steep Wave front signals, whereby the tops or peaks thereof are clipped. If the noise reduction action can anticipate the signal, as is possible in direct positive recording, this condition does not occur. However, to obtain duplicates of such a sound track, a negative must be printed, from which positives are made. These steps introduce distortion in the manner mentioned above.

With the increased use of magnetic recording, which does not require noise reduction, but which cannot be reproduced in standard theater equipment, photographic prints must be made from the magnetic records. Also, prints from direct positive Class B push-pull or printed Class A-B push-pull may be duplicated without distortion.

The present invention is directed to a system for electronically producing photographic prints of the above mentioned positive sound tracks and magnetic tracks. That is, the original track is reproduced by translatingl it into corresponding electrical signals which are impressed on a recording apparatus of the direct positive type, so that, upon normal development, a positive print reproducible with standard reproducers is obtained. This type of printing provides a higher quality print than contact printing, because, in addition to the inherent advantages of a direct positive track, it provides better definition of the high frequencies and has a lower distortion, since optical diffusion of the light through the negative iilm and poor printer contact will be eliminated. A better print is also obtained because speed variations which are invariably present in printers are reduced to a minimum, since the reproducers and recorders have better speed characteristics than printers. Furthermore, such a system does not require control units such as compressors, high and low pass filters, and dialogue equalizers. 'Ihe only equalizer desired is a lm loss equalizer which Will compensate for lm processing losses.

Electronic printing also has the advantage that all sounds which normally start With steep Wave fronts and decay slowly may be reproduced with a slowly rising starting wave front and an abrupt ending. This is accomplished by running the reproduced sound track backwards, as compared with the direction in which it was recorded. Furthermore, by this type of operation, clipping due to noise reduction action may be avoided in ninety percent of all recordings, since the sounds now start with a slowly rising Wave front. This permits the use of noise reduction ampliers in which the opening and closing times are almost the same. The opening time is made longer and the closing time is made shorter. This results, in eiect, in anticipatory noise reduction Without the use of additional equipment, since practically no clipping takes place any more. The shorter closing time also results in more effective noise reduction, since, due to the abrupt ending of sounds, nothing is gained by letting the noise reduction take hold slowly.

The principal object of the invention, therefore, is to facilitate the duplication of sound records.

Another object of the invention is to provide an improved system for producing photographic sound records from original sound records, either photographic or magnetic.

A further object of the invention is to provide an improved electronic printing or duplicating system for sound records.

A still further object of the invention is to provide a duplicating system for sound records .whereby improved records are produced.

AAlthough the novel features which are be- Fig. 3 shows a section of a direct positivesound record to be duplicated.

Fig. 4 is a section of a sound' track'electroni'cally printed from the sound track shown in Fig. 13 in accordance with the invention, and

Fig. 5 is a section of a sound track electronic.- ally printed from the sound track of Fig. 3 in accordance with a modication of the invention.

Referring now to Fig. 1,.1 an electronic printing system is shown diagrammatically. A sound track shown at' oria film G isscanned by a light beam from a lamp projected by lenses 8 and 9 to tliefilm 6 through the slit of va mask I0. This track may be a magnetic track, an original direct positive with anticipatory noise reduction, a direct Vpositive Class A push-pull, or a Class A-B push-pull printed from a negative, all of -which are-distortionless types of records. Only the'normal type of direct positive is reproducible in practically all standard theater systems, and thus', such a trackmust bev produced from the other track forms.

The emerging light from the sound track 5 is impressedon a photoelectric'cell I2 connected-to a photoelectric cell amplifier I3. The output of amplifier I3 is impressed on a film loss equalizer I5 yconnected to a gain control IS. The output of the gain control is impressed n a recording amplier I? and a recorder I8, which is-controlled by noise reduction amplier I9. The duplicate record is shown at 2B on film 2l and is of the type reproducible inY standard theater soundheads. By the arrows in- Fig. 1 Vad-jacent the films 6 and 2l, it is -indicatedthat the films are advanced upwardly, whichv represents that they are run kbackwards through the reproducer and recorder. In Fig. 2, the recorder I8 is shown impressing light on a film 23 to record-a sound track 2li, this nlm being run in a downward or the normal forward position. The remainder of the system oi Fig. 2 is the same as in Fig. 1.

First, as mentioned above, by this type of printing, a better sound track is produced than by contact printing of photographic records, where the light is impressed on the base of the film and passes through the negative to the positive, and is, therefore, diffused. This makes ity difficult to provide sharp definition of the high frequency modulations. Also, it is difiicult to maintain perfect contact between the lms at the printingv point because of the difference in length of a processedI negativeand raw stock, and any shifting between the negative and raw stock causes diffusion in the sound track images. Another advantage is that the sound track reproducer and recorder have inherently better speed motion than printers, and thus, the introduction of wows will be diminished. Also, only a lm-loss equalizer is required in the channel.

Also, as mentioned above, the positive film 6 with its sound track is run backwards through the reproducer, which means that the film isA started through the repro'ducer tail` end first. This is shown in Fig. 3,L whereby the-direction.- of

4 advancement of the film is indicated by the arrow, the upper end being the tail end of the sound record, and the lower end being the head end thereof. The record shown is a simple unilateral direct positive type of record with a shutter noise reduction envelope 25 to simplify the explanation. It will be noted inthis illustration that anticipatory noise reduction was applied as the shutter opened ahead of the position of the .rst peak 26.

By running the film backwards during reproduction, `and also, running the recorder backwards to record on film 2| the direct positive record shown at2, it will be noted that the slowly rising closing period of the noise reduction shutter can be readily recorded, while the head end of the record will take its normal closing time. Furthermore, since the new printing opening time .is at a slower rate (formerly the closing rate),

the opening rate can be lengthened so that the noise reduction amplifier can be timed so that the closing and opening rates are substantially the same, .thus providing a better over-all noise reduction. When records without noise reduction are'electronically printed to photographic prints, the noise reduction opening and closing times may still be substantially the same because the original records are run backwards, the slowly decaying endings reaching the light modulator first.

If it is desired to run the recorder forward, this may be accomplished by positioning the direct positive optics to record the track on the lefthand side of the record, as shown in Figs. 2 and 5. Normally, such a record would not be reproducible in the standard photographic reproducer unless the light is projected through the base of the lm, which is not desirable because of light diffusion. However, when the positive to be copied is reproduced tail end rst with reference to the recording operation, as shown in Figs. 1 and 3, the new sound track film 23 need only be reversed to advance it through the standard type of film reproducer.

With the above system, it is possible to restrict the use of the recorders solely to the electronic printing operation. This is accomplished in the system of Fig. 1 by restricting the running of the recorders to the backward direction. In view of the noise reduction timing values, original microphone recordings would have too many cycles of the starting modulations clipped to make the track commercial because of lengthened opening times. Also, if the system shown in Figs. 2 and 5, where the recorder is designed to run in the standard direction, is used, the track is on the wrong edge of the nlm for reproduction in a standard reproducer.

I claim:

l. A system for producing a positive sound record from an original positive sound record comprising means for translating said original sound record into electrical currents starting with the tail end of said original sound record, means for translating said electrical currents into light variations, meansA for impressing a photographic record medium with said light variations in the position on said medium of a normal record with said medium running in the same direction as said original sound record, and means for applying noise reduction to said light variations.

2. The method of claim, 1, in which means are provided vfor. applying said noise reduction with substantial equal .openingand closing times..

3. A system for producing a positive sound record from an original positive sound record comprising means for translating said original sound record into corresponding electrical currents starting from the tail end of said original record, means for translating said electrical currents into corresponding light variations, and means for impressing said light variations in the position on a photographic record medium of a normal negative record with said medium running in the opposite direction to that of said original sound record.

4. 'I'he method of claim 3, in which means are provided for applying noise reduction to said light variations, the opening and closing times of said noise reduction action being substantially equal.

5. A system for duplicating sound records comprising a sound record reproducer, means for advancing an original positive sound record through said reproducer tail end first, a direct positive sound recorder, a record medium, means for advancing said record medium through said recorder in the same direction as said original positive sound record, and means for impressing light variations corresponding to the modulations of said original record in a position on said medium normally occupied by a positive record.

6. A system in accordance with claim 5, in which a noise reduction unit is provided for said recorder, said unit having substantially equal opening and closing times.

7. A system of duplicating sound records comprising a sound record reproducer, means for advancing an original positive sound record through said reproducer tail end iirst', a direct positive sound recorder, a record medium, means for advancing said record medium through said recorder in a direction opposite to that of said original positive sound record, and means for impressing light variations corresponding to the modulations on said original record in a position on said medium normally occupied by a negative record.

8. A system in accordance with claim 7, in which a noise reduction unit is provided, said unit having substantially equal opening and closing times.

9. A system of duplicating sound records comprising a sound record reproducer, means for backwardly advancing an original positive sound record through said reproducer, a direct positive record, a record medium, means for advancing said record medium through said recorder forwardly, and means for impressing light variations corresponding to the modulations on said original positive record in a manner to produce a direct positive record upon normal development, said light being impressed in the position on said medium opposite to the position of a normal positive record.

KURT SINGER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,935,417 Robinson Nov. 14, 1933 2,414,666 Poulsen Jan. 21, 1947 2,512,785 Alburger June 27, 1950 

